This invention relates generally to pressurization systems, and more particularly to control of such systems.
Generally, a pressurization system may be constructed using a compressor and a pressure switch. In such a system, the compressor is typically configured to pressurize a gas, such as air, or a liquid. The pressure switch is configured to measure the pressure created by the compressor and turn the compressor on and off to maintain a desired pressure. In certain applications, it may be desirable to accurately or precisely control the pressure provided by the pressurization system. An exemplary application of a precisely controlled pressurization system may be a pressurization system that provides dry pressurized air to an antenna housing or radome to prevent the ingress of contamination, such as moisture. Such precision pressurization systems are often desirable as the housings or radomes used on many antennas are often fragile and easy fractured.
One approach to controlling pressure from a compressor uses a diaphragm pressure switch. A diaphragm pressure switch generally includes a diaphragm, a spring supporting the diaphragm, and a set of electrical contacts coupled to the diaphragm. Pressurized air in the system presses against the diaphragm, opposing a bias from the spring. Once the pressure reaches a desired point, the electrical contacts are opened, de-energizing the compressor. Later, as pressure in the system decreases, the contacts are closed, re-energizing the compressor and thereby maintaining a constant pressure in the system.
Diaphragm pressure switches are not particularly well suited to accurately regulating pressure due to the spring force within such switches varying with temperature, vibration, and wear due to cyclical use. Sample-to-sample consistency of springs may also impart unacceptable variations in pressure. Further, diaphragm pressure switches tend to be sensitive to gravity or physical orientation; therefore, implementation of a diaphragm pressure switch may be critical in accurately controlling pressure.
Other approaches for regulating pressure in a pressurization system involve the use of strain gauge transducers and microprocessors. In these approaches, a transducer may be used to provide a voltage that varies in proportion to the pressure in the system created by a compressor. The variable voltage from the transducer is then processed either directly or indirectly, after an analog-to-digital conversion is performed, by a microprocessor to control the operation of the compressor, thereby maintaining a given pressure.
Approaches utilizing transducers have the advantage of regulating pressure accurately but are of limited utility due to the microprocessors used therewith. Often, pressurization systems are needed in applications where moisture, vibration, and power consumption are of concern. Pressurization systems incorporating microprocessors in such applications may be prone to failure, while requiring additional power. Moreover, the use of a microprocessor in a pressurization system may increase the cost of such a system, sometimes prohibitively so.
Therefore, it would be desirable to provide a pressurization system having accurate pressure sensing and reliability. It would be further desirable to achieve such accuracy and reliability with reduced cost and power consumption.